A motor grader is an earth-moving machine generally employed as a finishing tool to sculpt a surface of a construction site or roadway to a desired shape and contour. A typical motor grader includes a front frame and a rear frame that are joined together at an articulation joint. The rear frame supports a power source, which is operatively coupled to rear wheels for primary propulsion of the motor grader. The rear wheels are arranged in tandem axles at opposing sides of the rear frame. The front frame includes a pair of front wheels and supports an operator station and a tool (e.g., a blade). The tool can be rotated, tilted, raised, lowered, and shifted side-to-side to a number of different positions. Steering of the motor grader is a function of both front wheel steering and articulation of the front frame relative to the rear frame. The operator station includes numerous hand controls used to steer the front wheels, position the tool, and control articulation.
Motor graders can be difficult to control effectively and require a highly skilled operator to produce desired surface contours. For example, in cul-de-sac grading, the operator is required to maneuver the motor grader around a substantially circular path while also maintaining the blade at a desired height and at a desired distance from curbs and other obstacles. This requires the operator to simultaneously control the blade, front wheel steering, and articulation. Failure to properly control articulation in such instances can result in the front and rear frames of the machine following separate travel paths, which can cause obstacle collisions or incomplete grading.
One attempt to simplify motor grader control is disclosed in U.S. Patent Publication No. 2011/0035109 of Ryerson et al. (“the '109 publication”). In particular, the '109 publication discloses a steering system with automated articulation control. The steering system includes a steering sensor configured to provide a signal indicative of a steering angle of a first frame, and a controller configured to calculate an articulation angle between the first frame and a second frame as a function of the steering angle such that a turning radius of the second frame matches a turning radius of the first frame.
Although the steering system of the '109 publication may help to simplify motor grader control, the steering system may still be less than optimal. Specifically, because the controller tries to match the turning radius of the first frame with the turning radius of the second frame, inaccuracies in articulation control may occur when steering of the machine transitions between curves having different radiuses (e.g., during machine travel along an S-shaped trajectory).
The disclosed articulation control system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.